[mythtv-users] coax vs. composite
adeffs.mythtv at gmail.com
Mon May 15 15:02:46 EDT 2006
On 5/15/06, Cory Papenfuss <papenfuss at juneau.me.vt.edu> wrote:
> >> When you say "coax" I assume you are referring to an RF signal with a
> >> TV signal modulated onto it. I mention this because "composite" video
> >> is normally carried on a co-axial cable.
> > Could you clarify this a bit? I always thought that "composite" video
> > was carried on a cable with RCA plugs at both ends, i.e. the same type
> > of cable that non-digital audio typically travels on. As far as I know,
> > this is NOT the same thing as coax. Which one of us is confused?
> > --Greg
> Coax is short for co-axial. All it means is that two wires are
> put together on the same center, rather than side-by-side, or
> side-by-side-twisted. Coaxial cable has a center conductor and a round
> shield around insulation placed around the center conductor... thus the
> co-axial part of the name.
> Whatever connector you put on this type of wire doesn't (much)
> matter. BNC, RCA, SMA, TNC, Type-R, Type-N, Type-GR, etc, etc... they are
> all forms of coaxial cable ends that can be placed on coaxial cable.
> Many people colloquially call RF-modulated TV signals coming in on 75 Ohm
> coaxial cable with Type-F ends "coax" for short. It's equally correct to
> call RCA patch cords for composite video "coax," but video patch cords
> with RCA ends typically carry composite video (i.e. non-RF modulated
> baseband video as described very well by a previous poster). Thus they
> are often colloquially called "composite" cables. Heck... it's generally
> even correct to call s-video "dual-coax" because all but the crappiest of
> s-video cables carry the chrominance and luminance signals separately on
> their own coaxial cables inside the main cable.
> Saying, "I connected my PVR-xxx to my STB via the coax connection"
> is a content-free statement regarding the *type* of connection between the
> STB and the capture card unless taken within this vernacular context.
> Hopefully thus endeth the confusion.
the confusion will never end, but that is a good writeup. We should
really put together a wiki page on this, with pictures, etc....
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